Technical Field
Embodiments of the subject matter disclosed herein relate to an exhaust gas recirculation system.
Discussion of Art
Exhaust gas recirculation (EGR) lowers peak combustion temperatures and hence lowers NOx production, and thus engine systems may be configured to tightly control EGR in order to maintain emissions under designated limits. Accurate control of the amount of EGR supplied to the engine relies on knowledge of the overall and/or fresh intake air flow to the engine. Particularly in engine systems that lack an intake air flow sensor, mechanisms for determining the intake air flow rate may be inaccurate, slow, and/or noisy, at least during some operating conditions, thus hindering accurate EGR control.
Brief Description
In one embodiment, a system comprises an engine having an intake manifold to receive fresh intake air and an exhaust gas recirculation (EGR) system to supply EGR to the intake manifold, where flow of EGR through the EGR system is controlled by one or more exhaust valves. The system further includes a controller configured to adjust a position of the one or more exhaust valves based on an estimated fresh intake air flow rate, where during a first set of operating conditions, the fresh intake air flow rate is estimated based on a total gas flow rate into the engine and further based on a current position of the one or more exhaust valves, intake manifold pressure, air-fuel ratio, and fuel flow to one or more cylinders of the engine.